Sopranos (divas) have a reputation of being difficult to work with. A popular joke is:
 
Q: What’s the difference between a soprano and a terrorist?
A: You can negotiate with a terrorist.
 
The form of the joke (“What’s the difference between a woman with PMS and a terrorist/”) has been cited in print since at least 1990. “What’s the difference between a soprano and the PLO?” was cited in 1993. “What’s the difference between a soprano and a terrorist?” was cited in 1997.
 
“What’s the difference between a pop star and a terrorist? You can negotiate with a terrorist” was said by Madonna in 2006.
 
 
Google Groups: rec.humor
What’s the difference between ...
Nick Nefedow
3/30/90
Q: What’s the difference between a woman with PMS and a terrorist ??
A: You can negotiate with a terrorist.
     
Google Books
List: Lots of List for Laughs and Lifts
By Derric Johnson
Yess Press
1993
Pg. XLVII:
Q. What’s the difference between a soprano and the PLO?
A. You can negotiate with the PLO.
 
Google Groups: rec.music.classical
Musician jokes v2.0
boB
9/1/94
(...)
Q: What’s the difference between a soprano and the P.L.O.?  A: You can negotiate with the P.L.O.
   
Google Groups: rec.music.bluenote
Let’s have some more music jokes!
David South, Jr.
9/7/95
(...)
What’s the difference between a soprano and the P.L.O.?
You can negotiate with the P.L.O.
 
Google Groups: rec.music.makers.choral
Choral Humour
Barbara Ruhmann
2/9/97
What’s the difference between a soprano and a terrorist?  You can negotiate with a terrorist!
 
Google Books
Getting Opera:
A Guide for the Cultured But Confused
By Matt Dobkin
New York, NY: Pocket Books (Simon & Schuster)
2000
Pg. 11:
What’s the difference between a soprano and a terrorist?
You can negotiate with a terrorist.
 
Google Books
The Mammoth Book of Humor
Edited by Geoff Tibballs
New York, NY: Carroll & Graf
2000
Pg. 218:
What’s the difference between a soprano and the PLO?
You can negotiate with the PLO.
 
Google Books
The Best Musicians’ Jokes
By Bruno Kassel and Carlo May
Pacific, MO: Mel Bay Publications, Inc.
2005
Pg. 68:
What’s the difference between a soprano and the PLO?
You can negotiate with the PLO.
 
Google News Archive
8 February 2006, Gettysburg (PA) Times, “Madonna jokes that pop stars are similar to terrorists,” pg. B5, col. 1:
NEW YORK (AP)—Madonna says she’s more stubborn than a terrorist—at least when it comes to her music career.
 
“What’s the difference between a pop star and a terrorist? You can negotiate with a terrorist,” jokes Madonna, poking fun at her diva reputation in the March issue of Harper’s Bazaar, which hits newsstands Feb. 21.